This invention relates to a captive panel fastener and more particularly, to such a fastener especially suitable for securing an aircraft panel and the like.
Aircraft captive panel fasteners are well known in the art. Conventionally, the fastener secures a panel to an aircraft by being inserted through an opening, which is smaller than the enlarged head of the fastener, of the panel and then engaged with a nut member attached to the base structure of the aircraft. To prevent the fastener from becoming displaced from the panel when the fastener is disengaged from the nut, the fastener is captivated to the panel by a retaining ring which carries integral keys or tabs that ride within keyways extending intermediate the ends of the fastener. After the fastener is inserted through the panel opening, the ring is snapped over the leading end of the fastener to engage the tabs with the keyways. One such panel fastener is shown in the U.S. Pat. No. 3,294,140.
A disadvantage of such prior panel fasteners is that the retaining ring must be relatively flexible and the tolerance between the ring and the fastener relatively loose to permit the tabs of the ring to be snapped over the leading end of the fastener and into the keyways. As a consequence, it has been found that in use, the retaining ring may accidentally snap off the fastener, particularly if the ring happens to be cocked at an angle when outward pressure is applied to the fastener. When this happens, the fastener may become dislodged from the panel and lost or could conceivably fall into a jet engine intake and possible damage the engine.
Although it has been known to slip a continuous rigid ring directly over the end of the fastener by extending the keyways through the end of the fastener and then afterwards inserting a flanged cap on the end of the fastener to retain the ring, installation of the flanged cap is objectionably time consuming.
It is also known to place a somewhat rigid, continuous ring on a fastener by deforming the tabs of the ring by bending them back during installation and subsequently straightening them into the keyways. However this is cumbersome and often results in a very loose fit between the ring and the fastener, as frequently the tabs are not fully straightened. Consequently, this type of ring also tends to become accidently displaced from the fastener.